Apparatus for continuous preparation of tobacco

ABSTRACT

Expanded Tobacco in a Continuous Process is disclosed. The apparatus comprises a continuously driven conveyor on which moist tobacco is carried, the conveyor passing through a freezing chamber and a drying chamber. Means are provided to circulate dry cool air at substantially atmospheric pressure within the drying chamber. There is also shown apparatus for continuously lifting soaking tobacco out of a body of water for subsequent freeze drying.

United States Patent 1191 Abbott et al.

[ 1 July 31, 1973 APPARATUS FOR CONTINUOUS PREPARATION OF TOBACCO [75] Inventors: John A. Abbott, Menlo Park; Clyde D. Watson, San Jose, both of Calif.

Related US. Application Data [62] Division of Ser. No. 884,850, Dec. 15, 1969, Pat. No.

FOREIGN PATENTS OR APPLICATIONS 1,815,169 7/1969 Gennany 131/140P OTHER PUBLICATIONS Freeze Dehydration Without Vacuum" Article in the magazine Meat, August 1963, pages 28, 29 and 50 cited.

r m fitqmin rrlfic P: R Attorney- F. W. Anderson, R. S. Kelly et al.

[57] ABSTRACT Expanded Tobacco in a Continuous Process is dis- [52] US. Cl 131/136, 131/140 P closed. The apparatus comprises a continuously driven [51] Int. Cl A24h 03/18 ccnvcycr on which moist tobacco is a the [58] Field of Search 131 140-144, 133, 136 vcycr p g through a fr zing ham r and a drying chamber. Means are provided to circulate dry cool air 56 R f s Ci at substantially atmospheric pressure within the drying UNITED STATES PATENTS chamber. There is also shown apparatus for continuously lifting soaking tobacco out of a body of water for 2,596,183 5/1952 Sowa 131/140 P subse em freeze d in 3,438,792 4/1969 Kruger 131 140 P ux q ry 10 Claims, 4 Drawing Figures COLD AIR INSULATION r1 ii o 13 a H\ T2 I 4 150. T REFmeERAroR 9 a V 8 msuumou BLWER PATENTE JUL 3 1 ms SHEET 2 BF 2 APPARATUS FOR CONTINUOUS PREPARATION OF TOBACCO The present application is a division of US. Pat. application Ser. No. 884,850 filed Dec. 15, 1969, now U.S. Pat. No. 3,704,716, and assigned to the assignee of the present invention.

BACKGROUND OF THE INVENTION There has recently been increased interest in the preparation of expanded tobacco for use in cigarettes. One reason for the interest lies in the increasing belief that some of the ingredients of cigarettes, such as tar and nicotine, may be harmful to smokers. It has been recognized that expanded tobacco, by virtue of the expansion thereof, will contain a correspondingly diminished amount of deleterious ingredients when used'in a cigarette of a given size. In other words, a cigarette containing expanded tobacco will contain less tobacco by weight, and hence less harmful ingredients, than a cigarette of the same size filled with unexpanded tobacco. Another recognized advantage for the producers of cigarettes of expanded tobacco is the reduction in the quantity of tobacco required to fill a given quantity of cigarettes.

It has been suggested that freeze drying of tobacco will produce a desirable expanded tobacco suitable for cigarettes. However, the tobacco industry requires a huge continuous supply of tobacco which cannot be supplied with conventional freeze drying apparatus unless a tremendous capital investment is made in vacuum equipment for conventional freeze drying.

In conventional freeze drying, a frozen article is placed in a vacuum chamber wherein heat is supplied to the frozen article to cause the mositure in the article to pass from the solid state to the gaseous state without passing through a liquid state. Normally, because of the high vacuumrequired, freeze drying is done by the limited volume batch process. Continuously supplying frozen tobacco to a vacuum chamber and continuously withdrawing tobacco therefrom would render it extremely expensive to maintain a sufficiently high vacuum in the chamber for the conventional freeze drying process.

SUMMARY OF THE INVENTION In the present invention, a continuous process, and apparatus therefor, is provided for the preparation of fibrous material, such as tobacco for cigarettes. In one feature of the invention, frozen tobacco is continuously supplied to a drying chamber through which cool air is circulated at essentially atmospheric pressure. The

moving air sweeps away the water vapor above the tobacco to reduce the pressure of the water vapor at the surface of the tobacco. In freeze drying, prompt removal of water vapor at the surface of the article is necessary for passage of the frozen moisture directly to the gaseous state, and a high vacuum, as used in conventional freeze drying, is useful to facilitate this transfer. But dry cool air blown past the article to sweep away water-vapor molecules as they reach the surface of the article can also be used, as described more fully in Science, Vol. 130, Sept. ll, 1959, pages 628-629, and in Meat, July and August 1963, pages 34 and 26, respectively. Frozen shredded tobacco, which has a high freezing point and a relatively large surface area per unit of mass is especially well suited tothis type of drymg.

In the present invention, frozen tobacco is moved continuously while being frozen, as through a freezing chamber, and while being freeze dried, as through a drying chamber through which cool air is circulated to atmospheric pressure. In the preferred form of the invention, the tobacco is only partially freeze dried, to save time, and is moved from the freeze drying chamber to a chamber for drying with air of higher temperature. Thereafter, the dried tobacco, which is now greatly expanded from its original state, is rehumidified to facilitate handling.

In its initial state, the tobacco is typically dry (with about a 10 to 13 percent moisture content) and in the form of shrunken shreds. The tobacco is first moistened for expansion, either by passing the tobacco under a water spray or floating the tobacco in a body of water. In the latter instance, a wire mesh conveyor passes through the surface of the water to raise and drain the water soaked tobacco. When the expanded tobacco is subsequently freeze dried as described above, the tobacco will remain in the expanded condition even after drying.

The tobacco is fed preferably by a continuously moving belt froma source of supply through the wetting step to a successionof separate chambers, in each of which a separate treatment is performed on the tobacco, so that fully processed tobacco is continuously delivered from the final downstream chamber.

It is therefore one object of the present invention to provide apparatus for the continuous freeze drying of shredded fibrous material to produce an expanded material.

It is another object of the present invention to provide for continuous freeze drying of tobacco at atmospheric pressure.

It is yet another object of the present invention to continuously soak tobacco and raise the tobacco for transfer into a freezer.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 2 is'a fragmentary plan view of the apparatus of FIG. I; and

FIG. 3 is a side view, in cross-section, of apparatus constructed according to one feature of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT There is shown in FIGS. 1A and 1B apparatus for continuously expanding tobacco for use in cigarettes. A conveyor 8, mounted on conveyor frame 9 (FIG. 2) has an endless wire mesh conveyor belt 10, with a horizontal upper run 11. Tobacco T1, which is shredded (to, say, 50 cuts per inch) and dry (say 10 to 13 percent moisture) is continuously deposited on the downstream end of the conveyor from a supply conveyor 12. A plurality of sprinkler manifolds 13 above the upper run 1 l of the belt extend across the conveyor to continuously discharge water on the belt 10, the tobacco Tl falling onto the belt, and the tobacco on the belt. On wetting,

the tobacco expands typically 2.6 times and contains 70 to 80 percent moisture. The wet, expanded tobacco is designated as T2.

The conveyor 8 extends through inlet and outlet openings 14a, 14b of an enclosed insulated freezing chamber 14 through which cold air, at about F, is cir' culated to freeze the wet tobacco which is continuously moving through the chamber 14 on the belt 10. The frozen tobacco is indicated as T3.

From the chamber 14, the conveyor 8 extends through inlet and outlet openings 15a, 15b of an insulated drying chamber 15. The chamber 15, which is enclosed, has an air inlet opening 16 in communication with an inlet duct 17 and has an outlet opening 18 in communication with an outlet duct 19. As shown schematically in FIG. 1A, air is drawn from chamber 15 and through duct 19 by a blower 20 connected to the duct 19. The blower 20 discharges air through a cooling chamber 21 where the air is cooled to typically 20 by a refrigerator unit 22. Moisture is condensed out of the air in the cooling chamber and when the air, which is carried through heater 23 to inlet duct 17, is subsequently heated in the heater to about 30, the air becomes very dry. The dry air from heater 23 passes into the inlet duct 17 for circulation through chamber 15. The final temperature of the air introduced to the chamber 15 can be regulated by the adjustable knob 24 on the electric power supply 25 which transmits electrical energy to the heating elements 26. Another method of supplying dry air would be to circulate the air through a bed of solid particulate dessicant, such as silica gel or materials known commercially as molecular sieves. Thus, dry (relative humidity less than percent) and cool air (about 30F) is continuously circulated through the chamber 15. Although air at the temperature and relative humidity indicated is preferred, it is only necessary that the air have a temperature and humidity so that the wet bulb temperature thereof is below the freezing point of the water soaked tobacco.

The dry cool air circulating through chamber penetrates the frozen tobacco T3 and sweeps away the water molecules from the surface of the shredded tobacco, which has a relatively large surface area. The rate of release of the water vapor from the frozen tobacco T3 is controlled primarily by the water vapor pressure at the surface of the tobacco rather than by total gas pressure. Although in conventional freeze drying, a vacuum is used to reduce the water-vapor pressure at the surface of the article being freeze-dried, the circulating dry, cool air will also effectively reduce the water-vapor pressure at the surface of material, such as the fibrous shredded tobacco. Thus, as in conventional freeze drying, the water vapor in the shredded tobacco will pass directly to gaseous vapor without passing through the liquid stage. This sublimation of the vapor in the tobacco will completely dry the tobacco, without shrinking the tobacco from the expanded state, if the continuously moving tobacco is exposed for a sufficiently long time to the cool dry air of the drying chamber 15, which, for convenience, may be referred to as a first drying chamber. If the tobacco is exposed for a lesser time to the air circulating through chamber 15, the tobacco will be only partially dried. The partially dried tobacco is indicated at T4.

In order to save time in the drying cycle, a second insulated drying chamber 30 may be provided, directly downstream (with respect to the direction of tobacco travel on the conveyor 8) from the first drying chamber 15. The conveyor 8 extends through inlet and outlet openings 30a, 30b in the chamber 30 and carries the tobacco through that chamber for completion of the drying. The drying is completed quickly by the circulation of warm (say 100F), dry (say I0 percent relative humidity) air through the chamber. Although air at the temperature and humidity indicated is preferred, it is only necessary that the air be at a temperature and humidity so that the wet bulb temperature thereof is above the freezing point of the partially freeze dried tobacco. The completely dried tobacco is indicated at T5. As the remaining vapor in the tobacco dries in chamber 30, the vapor passes through the liquid stage before finally evaporating. For this reason, it is preferable to freeze dry at least 90 percent of the moisture from the tobacco in chamber 15 so that there will not be a significant shrinkage of the tobacco when the remaining vapor passes through the liquid stage in chamber 30.

After the final drying, the tobacco is completely dry and brittle, although remaining in the expanded state of over twice the size of the original tobacco T1. In order to facilitate further handling, the tobacco moves on conveyor 8 through inlet opening and outlet opening 31a, 31b of an insulated rehumidifying chamber 31. Warm moisture air (of, for example, percent relative humidity and 80F) is circulated through the chamber to add moisture, say 10 to 13 percent, to the dry tobacco. The rehumidified tobacco is indicated at T6.

The tobacco thus is carried by the wire mesh conveyor successively and continuously through a wetting operation, and insulated chambers l4, 15, 30, 31 for separate treatment in each of the chambers while the tobacco is moved through the chambers. The tobacco in its processed form is continuously discharged through opening 31b of the final downstream chamber In lieu of wetting the tobacco by sprinkling, the tobacco Tl may, instead, be dropped into'a tank 40 from the supply conveyor 12. The tank 40 is filled with water which soaks the tobacco to a moisute content of 70 to percent. The downstream end of a conveyor 41 has a drum 42 mounted in the tank 40 below the surface of the water. An endless wire mesh conveyor belt 42, having an upper run 43 and a lower run 44, is received over drum 42. The wire mesh conveyor belt, which defines a continuous screen, has small closely spaced openings through which excess water drains. Two vertically spaced drums 45, 46 are positioned above the tank at the downstream end thereof. The upper run 43 of the conveyor belt is received over the upper drum 45 and the lower run 44 of the conveyor belt is received over the lower drum 46. The upper run 43 of the conveyor belt extends through a series of chambers similar to the construction shown in FIGS. 1A and 1B.

As a continuous supply of tobacco T1 drops 05 the end of supply conveyor 12, it floats on the water in the tank. The continuous supply of tobacco spreads across the water until the floating, soaked, tobacco contacts the wire mesh conveyor run 43 as it emerges through the surface of the water. The wetted tobacco T2 is then picked up and carried through the processing steps previously described in conjunction with FIGS. 1A and 18.

Although the best mode contemplated for carrying out the present invention has been herein shown 'and described, it will be apparent that modification and variation may be made without departing from what is regarded to be the subject matter of the invention.

What is claimed is:

1. Apparatus for freeze drying tobacco in a continuous process comprising in combination a conveyor to transport moist tobacco downstream, means for continuously driving said conveyor to transport said tobacco at a constant rate of speed, a freezing chamber in the path of the conveyor to freeze the moist tobacco thereon, a drying chamber in the path of the conveyor downstream from the freezing chamber, and means to circulate cool dry air at substantially atmospheric pressure through the drying chamber to freeze dry the frozen tobacco.

2. Apparatus for freeze drying tobacco in a continuous process comprising in combination a conveyor to transport moist tobacco downstream, means for continuously driving said conveyor to transport said tobacco at a constant rate of speed, a freezing chamber in the path of the conveyor to freeze the moist tobacco, a first drying chamber in the path of the conveyor downstream from the freezing chamber, means to circulate cool dry air at substantially atmospheric pressure through the drying chamber to partially freeze dry the frozen tobacco, a second drying chamber in the path of the conveyor, and means to circulate warm dry air at substantially atmospheric pressure through the second drying chamber to further dry the tobacco.

3. Apparatus according to claim 2 including a moistening chamber in the path of the conveyor and downstream from the second drying chamber to rehumidify the tobacco for handling.

4. Apparatus according to claim 3 including means for continuously driving said conveyor.

5. Apparatus according to claim 4 wherein said conveyor comprises an open mesh endless conveyor belt.

6. Apparatus according to claim 4 including means spaced upstream from said freezing chamber for continuously supplying wetted tobacco to said conveyor.

7. Apparatus for freeze drying tobacco in a continuous process comprising in combination a tank for containing a body of water and continuously receiving tobacco dumped therein, an open mesh endless conveyor belt with a lower run and an upper run for transporting moist tobacco downstream, said conveyor belt having its upstream end submerged beneath the surface of the water whereby the upper run of the conveyor belt is arranged to lift floating tobacco from said tank and to carry the tobacco to said freezing chamber, means for continuously driving said conveyor, a freezing chamber in the path of the conveyor to freeze the moist tobacco thereon, a drying chamber in the path of the conveyor downstream from the freezing chamber, and means to circulate cool dry air through the drying chamber to freeze dry the frozen tobacco.

8. Apparatus according to claim 7 including a second conveyor arranged to continuously dump tobacco into said tank.

9. Apparatus for freeze drying moist tobacco by a continuous process at a constant rate of freeze drying including a means for moistening thin shreds-of tobacco, a freezing chamber for freezing the moist tobacco, a freeze drying chamber, a tobacco conveying means passing through the tobacco moistening means and the freezing chamber and the freeze drying chamber in one continuous path, said freeze drying chamber being located downstream from the freezing chamber and said freezing chamber being located downstream from said tobacco moistening means, and an air cooling means for circulating within the freeze drying chamber cool dry air, said conveying means transporting the frozen tobacco into thermal communication with the cool dry air.

10. Apparatus for freeze drying moist tobacco by a continuous process including a freezing chamber for freezing moist thin shreds of tobacco therein, a freeze drying chamber, a tobacco conveying means passing through the freezing chamber and the freeze drying chamber along a substantially horizontal linear path, means for driving said conveying means at a constant linear speed, said freeze drying chamber being located downstream from the freezing chamber, and an air cooling means for circulating within the freeze drying chamber cool dry air at substantially atmospheric pressure thereby continuously freeze drying at a constant rate said tobacco which passes through said freeze dry ing chamber.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO. 3,749 ,l03

DATED July 31, I973 INVENTORG) I JOHN A. ABBOTT ET AL It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the abstract Insert before "expanded" Apparatus for the production of Column 2, line 6 change "to" to at I Column 4 I line 27 change "moisture" to moist Signed and sealed this 27th day of May 1.975.

(SEAL) Att St:

e c., MARSHALL D NN RUTH C. .MASON Commissioner of Patents Attesting Officer and Trademarks 

1. Apparatus for freeze drying tobacco in a continuous process comprising in combination a conveyor to transport moist tobacco downstream, means for continuously driving said conveyor to transport said tobacco at a constant rate of speed, a freezing chamber in the path of the conveyor to freeze the moist tobacco thereon, a drying chamber in the path of the conveyor downstream from the freezing chamber, and means to circulate cool dry air at substantially atmospheric pressure through the drying chamber to freeze dry the frozen tobacco.
 2. Apparatus for freeze drying tobacco in a continuous process comprising in combination a conveyor to transport moist tobacco downstream, means for continuously driving said conveyor to transport said tobacco at a constant rate of speed, a freezing chamber in the path of the conveyor to freeze the moist tobacco, a first drying chamber in the path of the conveyor downstream from the freezing chamber, means to circulate cool dry air at substantially atmospheric pressure through the drying chamber to partially freeze dry the frozen tobacco, a second drying chamber in the path of the conveyor, and means to circulate warm dry air at substantially atmospheric pressure through the second drying chamber to further dry the tobacco.
 3. Apparatus according to claim 2 including a moistening chamber in the path of the conveyor and downstream from the second drying chamber to rehumidify the tobacco for handling.
 4. Apparatus according to claim 3 including means for continuously driving said conveyor.
 5. Apparatus according to claim 4 wherein said conveyor comprises an open mesh endless conveyor belt.
 6. Apparatus according to claim 4 including means spaced upstream from said freezing chamber for continuously supplying wetted tobacco to said conveyor.
 7. Apparatus for freeze drying tobacco in a continuous process comprising in combination a tank for containing a body of water and continuously receiving tobacco dumped therein, an open mesh endless conveyor belt with a lower run and an upper run for transporting moist tobacco downstream, said conveyor belt having its upstream end submerged beneath the surface of the water whereby the upper run of the conveyor belt is arranged to lift floating tobacco from said tank and to carry the tobacco to said freezing chamber, means for continuously driving said conveyor, a freezing chamber in the path of the conveyor to freeze the moist tobacco thereon, a drying chamber in the path of the conveyor downstream from the freezing chamber, and means to circulate cool dry air through the drying chamber to freeze dry the frozen tobacco.
 8. Apparatus according to claim 7 including a second conveyor arranged to continuously dump tobacco into said tank.
 9. Apparatus for freeze drying moist tobacco by a continuous process at a constant rate of freeze drying including a means for moistening thin shreds of tobacco, a freezing chamber for freezing the moist tobacco, a freeze drying chamber, a tobacco conveying means passing through the tobacco moistening means and the freezing chamber and the freeze drying chamber in one continuous path, said freeze drying chamber being located downstream from the freezing chamber and said freezing chamber being located downstream from said tobacco moistening means, and an air cooling means for circulating within the freeze drying chamber cool dry air, said conveying means transporting the frozen tobacco into thermal communication with the cool dry air.
 10. Apparatus for freeze drying moist tobacco by a continuous process including a freezing chamber for freezing moist thin shreds of tobacco therein, a freeze drying chamber, a tobacco conveying means passing through the freezing chamber and the freeze drying chamber along a substantially horizontal linear path, means for driving said conveying means at a constant linear speed, said freeze drying chamber being located downstream from the freezing chamber, and an air cooling means for circulating within the freeze drying chamber cool dry air at substantially atmospheric pressure thereby continuously freeze drying at a constant rate said tobacco which passes through said freeze drying chamber. 